The present invention relates generally to a device for setting transfer roller engagement in an electrophotographic printing machine.
Generally, the process of electrophotographic printing and/or copying includes charging a photoconductive surface to a substantially uniform potential or voltage. The charged photoconductive surface is then exposed to record an electrostatic latent image thereon, which corresponds to an original document to be copied. Thereafter, a developer material is brought into contact with the latent image. The developer material attracts toner particles onto the latent image carried by the photoconductive surface. The resultant image is then transferred from the photoconductive surface onto a copy sheet, to which it is subsequently bonded.
In electrophotographic printing machines, such as printers and copiers, the photoconductive surface is typically carried by an electrically conductive substrate in the form of a conveyor belt or endless loop belt. Drive rollers engage the belt on the side thereof opposite the photoconductive surface. The drive rollers convey the belt carrying the photoconductive surface sequentially through stations within the electrophotographic printing machine that perform the various functions referred to above, i.e. charging, exposing, developing and transferring. To enable the drive rollers to convey the belt, tension is applied to the belt by tensioning rollers. A transfer roller is typically used to transfer the latent image from the photoconductive surface to the copy sheet.
The copy sheet is carried on the photoconductive surface of the belt and under the transfer roller. In order to ensure high-quality transfer of the latent image onto the copy sheet, the transfer roller engages the tensioned belt with a transfer force of a specified magnitude and directed generally perpendicular to the belt. As the copy sheet is carried under the transfer roller, this force presses the copy sheet against the photoconductive surface, and the latent image is transferred. The transfer force with which the transfer roller engages the belt displaces the belt in the direction of the force. The amount of this displacement is often measured to determine whether the transfer roller is engaging the belt with the specified force. This displacement measurement is often referred to as setting the transfer roller engagement.
Conventionally, the transfer roller engagement is measured with a linear variable differential transformer and an electrical interface board. However, as electrophotographic machines have become smaller in size, the space available for the equipment to measure the transfer roller engagement has become increasingly constrained. The relatively-large physical size of conventional equipment used to measure the transfer roller engagement have rendered their use incompatible with the latest generation of electrophotographic printing machines.
Therefore, what is needed in the art is a transfer roller engagement measuring device that is substantially more compact than conventional transfer roller engagement measuring devices.
The present invention provides an apparatus and method for measuring the deflection of a belt in an electrophotographic printing machine.
The invention comprises, in one form thereof, an elongate arm member having a first end and a second end. The second end engages and is displaced by the printing machine belt. A gearbox includes a plurality of gears interconnected into a gear arrangement, and a gearbox shaft coupled to the gear arrangement. The second end of the arm member is coupled to the gear arrangement, which converts displacement of the second end of the arm member to rotation of the gearbox shaft. An encoder is associated with the gearbox shaft. The encoder includes at least one encoder output. The encoder senses rotation of the gearbox shaft and issues electrical pulses on the encoder output. The electrical pulses are indicative of the direction and magnitude of the rotation of the gearbox shaft. A counter includes at least one counter input and at least one counter output. The counter input is electrically connected to the encoder output. The counter counts the electrical pulses and activates the counter output based at least in part upon the electrical pulses.
An advantage of the present invention is that it is substantially more compact than conventional transfer roller engagement measuring devices, and can therefore be used with the most advanced and modem electrophotographic printing machines.